This invention relates to covering materials for the structure of fluid medium craft, and more particularly, to a laminated plastic skin especially useful for aircraft and a method for applying the same to skeletal components of the craft.
In aircraft construction, weight, relative to lift, is generally the most critical parameter. Consequently, the airframe which includes the fuselage, airfoils, fin and stabilizer, etc., is covered by a skin-type material which is desirably light in weight and yet has the requisite strength in tension and shear to withstand the range of loading to which the aircraft will be subjected. Almost all commercially manufactured aircraft today are covered by metals such as aluminum or other lightweight alloys. Metal covering generally provides the best strength and the longest service life where cost is not a critical factor. However, it is heavier than non-metallic covers. Further, there exists today a significant segment of the aviation community involved with fabric or non-metallic covered airplanes.
Specifically, a significant number of flying enthusiasts in the general aviation community own or operate smaller aircraft which are totally or in part covered by a fabric-type skin. A commonly used fabric covering is comprised of a cotton linen which is placed over the frame and wetted to cause shrinkage and tautness, after which many layers of dope or lacquer are placed over the material to try to weatherproof it. A somewhat longer-lasting but more expensive covering are "Dacron" linens such as "Ceconite" or "Eonnex". Both of these, however, also require special coatings such as butyrate or acetate for weatherproofing and hardening. Also, all of these proposals require considerable labor and touching up between the application of multiple coatings so that the airfoil or fuselage has the proper amount of smoothness for minimum air drag. Finally, one or more layers of an appropriate coloring material are required to provide the desired color for that portion. One disadvantage of a fabric or linen wing is its propensity to tear or puncture if it accidentally comes into contact with a blunt object. Also, a uniform wetting and hence shrinking is not easily obtained. Where the shrinkage is nonuniform, wrinkles will occur which are extremely difficult to eliminate. All of these factors are extremely critical to the performance of the airframe portion as an airfoil and hence affect the ultimate performance of the aircraft itself.
In addition, a great number of these older airplanes are not hangered and hence subjected continually to the weather elements. The multitude of layers of lacquer or dope are not only intended to provide additional strength and rigidity to the fabric but also to provide somewhat of a protective coating against the weather. In addition to the weather elements of precipitation and wind, there is also the problem of ultraviolet deterioration caused by ultraviolet rays received from the sun. If the fabric or covering is not sufficiently protected from ultraviolet deterioration, the covering will embrittle and lose its strength. All of these foregoing factors determine the particular service life and safety of a particular covering.
There is a real need today in the aviation industry for an improved airframe covering material which is stronger, lasts longer and is relatively less expensive compared to present proposals. Safety after a considerable time period is most important. There is also a need for such a covering material which is considerably easier and cheaper to install.